Sang 1989;57:185-7. The Changing Spectrum of Fever of Unknown Origin in

SIR-We retrospectively reviewed the files of77 patients with a fever of unknown origin (FUO), diagnosed according to the defi-nition of Petersdorf and Beeson [I], at the time of admission to the National Institute of Nutrition (NIN) in Mexico City. Re-ports of two previous studies [2, 3] published by investigators at NIN described 120 patients who presented during a period of27 years (4.44 cases/year). The findings of those studies were simi-lar to the information in the literature [1]: infections were the most common etiologies (48.3%), followed by neoplasia (23.3%) and connective-tissue diseases (12.5%). The most frequent in-fectious cause of FUO before 1970 was amebic hepatic abscess (AHA) (32.4 % of all infections), but in the 1970s, tuberculosis (TB) emerged as the most important infectious etiology (14.5%). The most common neoplasia then was lymphoma (64.3%), and systemic lupus erythematosus was the most important connec